Reaction motor operable by liquid propellants and method of operating it



MALINA ETAL REACTION MOTOR OPERABLE BY LIQUID PROPELLANTS Oct. 30, 1951F. J.

AND METHOD OF OPERATING IT Filed May 8, 1945 OX/D/ZER INERT 6A5JOH/VWPARM/VS FRANK J MAL/NA PRESSURE REG ULA T0}? FUEL IN VEN TORS,

BY I

AGENT Patented Oct. 30, 1951 REACTION MOTOR OPERABLE BY LIQUIDPROPELLANTS AND METHOD OF OPER- ATING IT Frank J. Malina and John W.Parsons, Pasadena,

Calif., assignors to Aerojet Engineering Corporation, A zusa, Calif.,

a corporation of Delaware Application May 8, 1943, Serial No. 486,236

Claims.

Our invention relates to jet propulsion and more particularly topropellants which are useful in connection therewith.

While our invention is capable of use in connection with the propulsionof a wide variety of different devices and vehicles, since it findsparticular utility in the propulsion of aircraft, its advantages aredescribed with relation to such use, it being understood that ourinvention is, however not limited to such use.

Prior to our invention special means were always required to ignite thepropellants. For example, when liquid oxygen is used as an oxidizer andgasoline is used as a fuel, some auxiliary ignition means must always beprovided to initiate combustion of the propellants. This isobjectionable because it requires either a spark plug or other i-gnitoror means for heating the walls of the combustion chamber above theignition point of the propellant mixture making this system complex anddependent upon the operation of such ignition system.

While spontaneous combustion is obtained with our preferred combinationsof propellants which is especially effective when operating inaccordance with our preferred method it will be understood that thepropellants we have discovered offer advantages even when operatingunder other conditions.

The present invention relates to fuels, and oxidizers and theircombination as propellants and their method of injection into a jetmotor. Among the objects of our invention are: to provide more eificientand eiiective propellants for jet propulsion systems; to provide anoxidizing agent which is easily combustible with a suitable fuel andwhich has a large amount of oxygen available for burning a fuel; toprovide propellants, that is, fuels and oxidizers, which arespontaneously combustible; to provide a method for utilizing suchpropellants to give smooth combustion and to eliminate danger ofexplosion; to obviate the difiiculties attendant upon the use ofliquified gases; to eliminate the need of an auxiliary ignition systemto ignite the propellants.

oxidizers As a result of a thorough investigation of the variousoxidizing agents which may be used as propellants we prefer to employnitric acid. Since water tends to retard combustion of the acid with anyfuel, the nitric acid should be substantially free of water. Thus, whitefuming nitric acid, which normally contai s less than (01. lac-35.6)

about 2% of water by weight, is to be preferred to weaker solutions ofnitric acid. However, we

have found that more dilute solutions of nitric acid may be utilizedprovided that nitrogen di- 5 oxide is dissolved in the nitric acid;which is a way of increasing the concentration of an otherwise moredilute solution. Preferably the nitric acid should contain at leastabout 5% N02 but preferably at least about to N02. Such a solution ofnitrogen dioxide is known as red fuming nitric acid and almost all redfuming nitric acid which is commercially available in this countrycontains between about 5% and 20% nitrogen dioxide by weight and lessthan about 5% water by weight. Specifications for nitric acid,obtainable commercially as red fuming nitric acid, are as follows:

Chemical composition:

HNOa, 90.5% by weight minimum. Water, 2.5% by weight maximum. N02, 7.25%by weight maximum-6.50% by weight minimum.

Physical properties:

Density, 1.5 minimum1.55 maximum 70 F. Melting point, -50 F. maximum.Color, etc., orange to dark red-fume s vigorously when exposed to air.

Specifications for nitric acid, obtainable commercially as white fumingnitric acid, are as follows:

Chemical composition:

Nitric acid, 97.5% by weight minimum. Water, 2.0% by weight maximum. N02content, 0.5% by weight maximum.

Physical properties:

Density, 1.46 minimum1.52 maximum 68 F. Melting point F. Color, etc.,straw yellow to water white;

fumes vigorously when exposed to air.

found that liquid nitrogen dioxide is a very satis- Y factory oxidizer.

agents hereinabove mentioned and which are satisfactory for jetpropulsion provided that the propellants are supplied to I thecombustion.

chamber under suitable operating conditions.

These operating conditions are discussed more in detail hereinbelow.

We have found that the four groupsof compounds listed below may beutilized as fuels.

These groups are listed in the order of their effectiveness. I

Grou I.Liquid organic compounds containing at least one amine radical,such as,

A. Aniline, orthotoluidine, and methylamine,

B. Liquid hydrocarbons, containing large percentages of such aminesubstituted. organic compounds.

Group II.Highly unsaturated hydrocarbons: iquidhy arbons of th ace yl tye and containin a large fraction of unsaturated (double and triple)carbon bonds, or both, for example, divinyl acetylene, dipropargyl, andpropargyl alcohol.

Group III'.Liquid substances containing the v elements having theproperties of lithium (Li), berillium (Be), boron (LB), aluminum (Al)magnesium (Mg), phosphorus 1?), potassium (k),

and sodium (Na). With the exception of phosphorus all of theforegoingelements are particularly useful in fuels because they generatelarge amounts of heat during. combustion, and phosphorus is.particularly-useful because it has a low ignition. temperature. I

A. Liquid hydrides of those elements. I B. Liquid organo-metalliccompounds containing one or more of such elements. C. Liquid fuelscontaining one ormore such elements. D. Liquid fuels containinsone: ormore such elements in susp n i n- Group IV.Organic compounds having thep p rties-of pyrole pyridine pinene terpene pinole terpinol hydrazineozonides V carbon disulphide containing phosphorus.

All the above identifiedsubstances are spontaneously combustible withthe. oxidizers hereinbefore discussed. andare independently useful withother oxidizers where means for ignition is provided.

s e-s w Of all of these fuels we prefer to. employ the While during theinitial combustion, and subsequent propellants.

inject propellants into the combustion chamber Method of operation Theabove mentioned oxidizers and fuels may be used together as pairs ofspontaneously combustible propellants at atmospheric temperature andpressure. However, if desired these oxidizers and fuels may be used withother fuels (such as gasoline) or other oxidizers (such as liquidoxygen) respectively.

So far as we know we are the first to achieve spontaneous combustion injet propulsion systems at the temperature and pressure of the mediumsurrounding the jet motor and while other fuels and oxidizers might beutilized to accomplishsuch spontaneous combustion we prefer to. use thefuels; and oxidizers hereinbefore mentioned. 7

j. Certain difficulties are encountered when utilizing. thesepropellants for propulsion. Unless the propellants are supplied to thejet motor under the proper conditions the motor is liable to failcompletely, to pulsate in its ope'ration','-or to explode, even thoughthe propellants ares'up-"f plied at uniform rates. e

These difficulties may be eliminated and certainty and smoothness ofoperation secured by} so relating the rates of injection of fuel andoxidizer to the-size of'the' jetchamber and the inherent ignitionproperties of the mixturethat explosion of the combustible mixtureisavoided injection occurs at rates conducive to the'combustion of thecontinuously supplied propellants so as to avoid the accumulation in thejet chainber of any substantial amount of the unburned To achieve thisresult, we initially 9 at rates such that the amount of propellants injected' prior to the initiation of combustionjisf less than about 20% ofthe volume of the combustion chamber.

After combustion has been'initiated', the pro-=- pellants may beinjected at a greater'rate than they are injected initially inasmuch as.the time interval between their injection and combustion is reducedbecauseof the higher temperatureand pressure ofthe mixture resultingfrom prior combustion and the; heating of the. walls-0f the. combustionchamber by; the products ofcombustion.

In. the drawing the figure shows a jet motor system including tanks andconduits for supplying propellants to the motor.

The fuels and oxidizers hereinbefore dc.- scribed are advantageously.employed'in the pro-,- pulsionof an aircraft by providing the-fuelandoxidizer in separate containers H and I2 rein to the receptacles IIand llandi 'provided with a gas under pressure, preferably a gas inertwith respect to either propellant. Preferably the container for the fueland the container for the oxidizer are connected toa source of pressureadapted to force the" contents ofsueh containers into. the jetor'combustion chamber-at controlled rates determined by the degree ofopening of the valves in said pipes.

The practice of the method of our invention contemplates so relatingthe. rates of injection" of the oxidizer and of the fuel to thecombustion or jet chamber to their inherent combustion properties andthe size and temperature of the chamber that smooth non-explosivecombustion occurs initially and throughout the entire operation Whileproviding the desired quantity of propulsive power. Our invention isparticularly advantageous when the combustion chamber is initially atatmospheric temperature, or at the temperature of any other medium inwhich the motor is to operate, as We are able to achieve combustioninitially without auxiliary ignition or preheating of the chamber or thepropellants.

If the propellants are supplied at such initial rates, then, when thepropellants are initially injected into the jet motor, the initiallyburned propellants soon fill the combustion chamber with hightemperature gases and vapors which heat the incoming propel ants therebyvaporizing them and reducing the ignition time lag. Then thesubsequently injected propellants burn spontaneously without anysubstantial accumulation of propellants in the liquid phase.

As an example, applied to a combustion chamber having a length of aboutinches and a cross sectional area of about 7 square inches, highlyconcentrated nitric acid and aniline operate very satisfactorily whenthey are injected into the combustion chamber initially and prior tocombustion at the rates of 3.6 lbs. per second and 2.4 lbs. per secondrespectively.

While these propellants and method of use and the apparatus for theiruse in propelling aircraft or other devices, which are hereinbeforedescribed, are fully capable of providing the advantages primarilystated, it will be recognized by those skilled in the art that variousmodifications and alterations may be made therein while still providingsuch advantages, and our invention is therefore to be understood as notlimited to the specific embodiments hereinbefore described but asincluding all modifications and variations thereof coming within thescope of the claims which follow.

We claim as our invention:

1. Means for supplying propellants to a reaction motor, including: twocontainers; a fuel in one of said containers, said fuel comprising aliquid organic compound of the group consisting of aniline,orthotoluidine, and methylamine; a liquid oxidizer consisting of redfuming nitric acid, white fuming nitric acid, and nitrogen dioxide inthe other of said containers, said fuel and oxidizer being adapted forspontaneous combustion when mixed in such reaction motor at thetemperature and pressure of the medium surrounding said reaction motor;and means for separately and simultaneous injecting said liquids intothe motor.

2. Means for supplying propellants to a reaction motor, including: twocontainers connected to such reaction motor; aniline in one of saidcontainers; an oxidizer consisting of red fuming nitric acid, whitefuming nitric acid, and nitrogen dioxide in the other of saidcontainers, said aniline and oxidizer being adapted for combustion whenmixed in such reaction motor; and means for separately andsimultaneously injecting said aniline and oxidizer into said motor.

3. The method of propelling a device having a combustion chamber, whichincludes the steps of supplying aniline to the combustion chamber, andsimultaneously supplying to the combustion chamber nitric acid which issubstantially free of water, and causing the products of the sponta- 6;neous reaction betweensaid aniline and said nitric acid to escape fromsaid combustion chamber to produce a reaction thrust on said device.

4. The method of developing thrust which comprises impinging anilineandnitric acid from the group consisting of red fuming nitric acid andwhite fuming nitric acidagainst each other in a chamber whichis closedexcept for a constricted exhaust nozzle, and expelling the resultantreaction products through said nozzle to produce a reaction thrust onsaid chamber.

5. The method of developing thrust which comprises impingingorthotoluidine and nitric acid from the group consisting of red fumingnitric acid and white fuming nitric acid against each other in a chamberwhich is closed except for a constricted exhaust nozzle, and expellingthe resultant reaction products through said nozzle to produce areaction thrust on said chamber.

6. The method of developing thrust which comprises impinging methylamineand nitric acid from the group consisting of red fuming nitric acid andwhite fuming nitric acid against each other in a chamber which is closedexcept for a constricted exhaust nozzle, and expelling the resultantreaction products through said nozzle to produce a reaction thrust onsaid chamber.

7. The method of developing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion in said reaction chamber of aniline and nitric acid from thegroup consisting of red fuming nitric acid and white fuming nitric acid.

8. The method of propelling a device having a combustion chamber whichincludes the steps of supplying aniline to the chamber andsimultaneously supplying to the chamber nitric acid containing N02 andnot more than about 2% water, and causing the products of thespontaneous reaction between the aniline and the acid to escape from thechamber to produce a reaction thrust on the device.

9. The method of developing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion in said chamber of aniline and red fuming nitric acid.

10. The method of developing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion in said reaction chamber of a liquid organic compound of thegroup consisting of aniline, orthotoluidine and methyl amine with aliquid oxidizer selected from the class of compounds consisting ofnitrogen dioxide and nitric acid containing N02 and not more than about2% water.

FRANK J. MALINA. JOHN W. PARSONS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 254,021 Johnston Feb. 21, 1882914,624 Winand Mar. 9, 1909 1,305,340 Bostedo June 3, 1919 1,405,482Bostedo Feb. '7, 1922 1,506,322 ONeill Aug. 26, 1924 1,506,323 O'NeillAug. 26, 1924 1,532,930 ONeill Apr. 7, 1925 2,474,183 King June 21, 1949(Other references on following page) Number FOREIGN PATEN'IS.

OTHER REFERENCES Bflstein, Handbuch der- Crganischefi cngni Countr- DateieQ' Qth edition; v01. 1-, page454. itg- 17 1915 Organic Chemistry byWhitmore; D. V611? Great Britain Jan 1934 Nostrand, Inca, C., 1937,Reprint-I937-,P E- Great Britain "Dec. 3, 1937 5 7441 1 France Jan; -4"The'lnteractronrofDimethylamlmeand-Nltr m- Switzerland 1, 93 Acid by H.Hodgson and Gerald 'Iurner in the Journal; of the Chemical Society,pfiblished 1942 by the' C1Iem1ca1' Society; London, pagea-

